Choice "D" is correct. Under Article 2 an offer can be accepted by a promise to ship or by prompt shipment. Shipment of nonconforming goods constitutes both an acceptance and a breach unless a notice is sent prior to shipping that the goods are only an accommodation.
Choice "c" is incorrect. Shipment of nonconforming goods is not a counteroffer unless accompanied by a notice of accommodation. Here, Handy shipped the socket sets without any explanation concerning the shipment.
Choice "b" is incorrect. In a goods contract, acceptance of an offer can be made merely by shipping goods.
Choice "a" is incorrect. Shipment of goods is an acceptance, whether or not the goods conform. If they do not conform, the shipment is also a breach.